1. Field of the Invention
This invention relates to an apparatus for surface treatment by electrolytic polishing or electroplating for workpieces contained in a barrel container.
2. Description of the Prior Art
In known apparatus for barrel polishing, the polishing is performed by abrasion of workpieces with an abrasive. Prior art has provided an electrolytic barrel polishing apparatus wherein the conventional barrel polishing apparatus is provided with anode and cathode plates so that an electrochemical polishing can be performed together with the above-described polishing by the abrasion. Japanese Published Patent Application (Kokoku) No. 45-26360 (1970) and 46-9916 (1971) each discloses such a electrolytic barrel polishing apparatus. In the disclosed apparatus, an anode and a cathode are disposed in the barrel so as to be away from each other and an electric circuit is made so that workpieces serve as the anode.
The workpieces are usually caused to serve as the anode in the electrolytic polishing. On the contrary, when the workpieces are caused to serve as the cathode, an electroplating can be performed. Thus, the electrolytic polishing is a technique closely related to the electroplating. The prior art has provided for several types of electroplating apparatus employing a barrel. For example, Japanese Published Utility Model Registration Application (Kokoku) No. 56-55252 (1981) discloses one of such electroplating apparatus employing the barrel. In the disclosed apparatus, a tub vibratory machine is supported by springs. A cathode plate is provided in the barrel so that a distal end thereof reaches the barrel bottom where the workpieces are reserved while an anode plate is hung to be opposed to the cathode plate.
Supplying a large current to the workpieces with voltage drop between electrodes is an important factor from the viewpoints of treatment efficiency and consumed electric power. However, the anode and cathode plates are disposed in the barrel to be away from each other in the abovedescribed conventional apparatus. Accordingly, the current necessary for the electrolytic polishing or the electroplating cannot be obtained unless the supplied voltage is increased. That is, a desired polishing quality such as the gloss, deburring or thickness of plated coating cannot be obtained within a predetermined period of time when a small current is supplied to the apparatus. However, the temperature of the electrolyte is raised by a Joule's heat when an excessively high voltage is applied.